As is well known, antitumor antibiotic agents can be produced via the fermentation of a variety of microorganisms. Antibiotic tropolone compounds were discussed by Nozoe et al in "Synthesis of Puberulonic Acid", Bull. Chem. Soc. Japan, 33 (1960) pp. 1071-4.
In 1981 and 1983, researchers reported on the action of colchicine and analogs thereof in treating P388 leukemia in mice See Quinn et al, "Quantitative Structure--Activity Relationships of Colchicines against P388 Leukemia in Mice", J. Med. Chem., 24 (1981) pp. 251-6 and Brossi et al, "Biological Effects of Modified Colchicines . . . ", J. Med. Chem., 26 (1983) pp. 1365-9.
U.S. Pat. No. 4,656,192 to Yamato discloses alkyl- and hydroxy-substituted tropolones and their use as antitumor agents.
Synthesis and antitumor activity of compounds containing two tropolone moieties are described by Yamamoto et al., "Synthesis and antitumor activity of tropolone derivatives . . . ", J. Med. Chem., 35 (1992) pp. 267-273. A natural product containing two tropolone units has been isolated by Sasade et al., "Structure of Fusariocin C. . . .", Agric. Biol. Chem., 45 (1981) pp. 1689-1692.